1. Field of the Invention
This invention relates to a fluid-impermeable composite hose. More particularly, it relates to a fluid-impermeable composite hose having a fluid-impermeable layer formed by sandwiching between two thin resin layers a laminated layer containing a metallic foil, or a metallic layer formed by vapor deposition. The hose of this invention is particularly suitable for use on a motor vehicle as a hose for transporting a refrigerant, such as carbon dioxide, or as a fuel hose.
2. Description of the Related Art
It is strongly desired in view of system maintenance, environmental protection, etc. that every hose used for transporting a refrigerant, such as carbon dioxide, in an air-conditioning system on a motor vehicle be impermeable to the refrigerant. One of the most effective approaches lies in a hose having a laminated wall layer which contains a metallic foil, or a metallic layer formed by vapor deposition. Environmental protection also requires a fuel hose to be impermeable to fuel, and a laminated wall layer is very useful for a fuel hose, too.
When making a hose having such a laminated layer in its wall, it has hitherto been usual to form, for example, a rubber layer having high refrigerant or fuel resistance and impermeability inwardly of such a laminated layer. For making a hose required to withstand a high pressure, it has been usual to surround such a laminated layer by an intermediate rubber layer, etc., then by a reinforcing yarn layer and finally by an outer rubber layer.
The laminated layer employed as described is, however, not thoroughly secured or reinforced in the wall of the hose. Therefore, it is directly affected by any bending, deforming or stretching force acting upon the wall of the hose as a result of e.g. an elevation in pressure of the refrigerant in the hose, the vibration of the vehicle, or any impact bearing upon it. Thus, the metallic foil or layer in the laminated layer is easily broken and the hose loses its fluid impermeability.
It is, therefore, an object of this invention to prevent effectively any breakage of a metallic foil or layer in a laminated layer of a fluid-impermeable composite hose. The inventors of this invention have thought that it is very effective to sandwich a laminated layer between two thin resin layers, and that the hose is flexible enough if those resin layers are adequate.
According to a first aspect of this invention, there is provided a hose having a wall comprising a fluid-impermeable layer of a sandwiched structure in which a laminated layer is held between two thin resin layers, the laminated layer containing a metallic foil, or a metallic layer formed by vapor deposition. The laminated layer is secured and protected by the two thin resin layers located radially inwardly and outwardly thereof. The bending, deforming or stretching force acting upon the hose for various reasons is absorbed or diminished by those resin layers, and is not directly transmitted to the laminated layer. No force acts upon the metallic foil or layer in the laminated layer to twist, bend, stretch or otherwise deform it. Thus, the metallic foil or layer is not easily broken, and the hose does not lose its fluid impermeability.
According to a second aspect of this invention, the fluid-impermeable layer forms the innermost layer of the wall of the hose. The thin resin layer on the inside of the fluid-impermeable layer is superior to any rubber layer in refrigerant impermeability. Unlike a rubber layer, it does not deteriorate by swelling or foaming even when carbon dioxide as a refrigerant is in its supercritical state at a high temperature and a high pressure. Thus, the hose is particularly suitable as a hose for transporting carbon dioxide as a refrigerant for e.g. an air conditioner on a motor vehicle.
According to a third aspect of this invention, the wall has a rubber layer inwardly of the fluid-impermeable layer. Such a layer can be of a material having a high resistance to swelling with fuel and a high impermeability to fuel, such as fluororubber (FKM) or acrylonitrile-butadiene rubber (NBR), so that the hose may be suitable as a fuel hose.
According to a fourth aspect of this invention, the wall has a reinforcing layer and an outer rubber layer outwardly of the fluid-impermeable layer. The reinforcing layer gives pressure resistance and strength to the hose. The outer rubber layer gives ozone resistance to the hose, protects it from any external impact, and improves the tightness of a seal in a joint between the hose and a pipe.
According to a fifth aspect of this invention, the wall has an intermediate rubber layer interposed between the fluid-impermeable layer and the reinforcing layer. The intermediate rubber layer gives an improved adhesion between the fluid-impermeable layer and the reinforcing layer, diminishes any bending, deforming or stretching force acting upon the fluid-impermeable layer, and improves the flexibility of the hose as a whole.
According to a sixth aspect of this invention, the laminated layer is formed by spirally winding or longitudinally lapping a tape of a laminated sheet containing one of the following (1) to (3) and a resin film or films laminated thereon:
(1) a metallic foil;
(2) a metallic foil and a reinforcing material; and
(3) a metallic layer formed by vapor deposition.
The resin film (or films) protects the metallic foil or layer when the hose is bent, deformed or stretched. The metallic foil or layer is not easily damaged or broken by fatigue, and the hose maintains its high fluid impermeability for a long time. Spiral winding or longitudinal lapping makes it very easy to form the laminated layer on a tubular hose body. If the laminated sheet contains a metallic foil and a reinforcing material, its stretch resistance makes it possible to avoid the breakage of the foil even if the hose may be stretched or bent by a force which is too strong to be resisted by the resin film (or films) alone.
According to a seventh aspect of this invention, at least one of the thin resin layers on the inside and outside of the fluid-impermeable layer is of an ethylene-vinyl alcohol copolymer resin (EVOH), a blend of a polyamide and a modified polyolefin resin, a polyamide resin, or a fluororesin. All of these resins are high in fluid impermeability for refrigerant or fuel and in flexibility, so that the hose has a still higher fluid impermeability, and is flexible enough to withstand the vibration of a motor vehicle, or its engine.
According to an eighth aspect of this invention, at least one of the thin resin layers on the inside and outside of the fluid-impermeable layer has a thickness of 20 to 300 xcexcm. This is a preferred range in which the resin layers can perform its protective action effectively and thus ensure the fluid impermeability without affecting the flexibility of the hose in any way.
The above and other features and advantages of this invention will become more apparent from the following description and the accompanying drawings.